The San Francisco Board of Supervisors this afternoon voted to become the first city to prohibit the use of petroleum-based plastic carry out bags in grocery stores and other large market stores.

The Board approved the measure 10-1; the first of two votes needed for final passage of the measure. Supervisor Ross Mirkarimi sponsored the legislation mandating the use of compostable plastic bags or recyclable paper bags, and that would affect grocery stores in six months and large drugstore chains in a year.